With all the recent talk about Android KitKat, I thought I was late to the party. So I went looking today. Still there is not much in it. I took the opportunity anyway to quickly summarize the API changes that are probably worth noting for an Android developer. Here is that search trace below. You will high level features by each of the sub JellyBean releases and I have also listed all the changed/new APIs in a single list for all of 4.x releases so far at the end.
satya - 9/13/2013 11:49:57 AM
Android kit kat release
Android kit kat release
satya - 9/13/2013 11:54:13 AM
An early anticipation from gotta-be-mobile
satya - 9/13/2013 11:56:09 AM
Android KitKat will be 4.4
4.1 - Jelly bean
4.2 - Jelly bean
4.3 - Jelly bean
satya - 9/13/2013 2:22:45 PM
4.1 enhancemetns
faster, smoother, more responsive
triple buffering, cpu input boost, vsync
Enhanced accessability (need to understand more!)
Significantly Updated Notifications framework
bigger, richer, more buttons
Resizable widgets
Ability to use manifest file for navigating between activities
Task Stack Builder
to provide a consistent task context for activities
even when they are invoked by themselves
More remoteable views
Changes to animations
Render Script enhanced
Javascript V8
Google cloud messaging
Smart app updates
Integrated google services such as google+
Google Play Services SDK
satya - 9/13/2013 2:40:04 PM
4.2 enhancements
hardware accelerated 2D renderer
webview is optimized
Support for multiple users
App widgets on lock screens
Daydreams: activities that are specialized to run
when device is docked like a screen saver with attitude
Your app can offer some day dreams in the manifest
Display Manager API to work with multiple displays
Nested fragments
Build in developer options and user interaction
bug reports
A number of Security features including app verification
satya - 9/13/2013 2:46:40 PM
4.3 features
opengl es 3.0
extended/polished multiuser support
Modular DRM framework
Ability to subscribe to notifications
satya - 9/13/2013 4:36:58 PM
4.1 (API 16) Key APIs
isolated services
App Stack Navigation
Copy and Paste
Notifications
Animations
New Remote Views
satya - 9/13/2013 4:42:58 PM
4.2 (API 17) Key APIs
daydream
Lockscreen widgets
multiple users
multi screen
Nested fragments
satya - 9/13/2013 4:45:13 PM
4.3 (API 18) Key APIs
ES 3.0
Restricted profiles
View Overlays
Notification listeners
satya - 9/13/2013 4:46:22 PM
Taken together key Jelly Bean APIs
Isolated services
App Stack Navigation
Copy and Paste
Notifications, Notification listeners
Animations
New Remote Views
daydream
Lockscreen widgets
multiple users
multi screen
Nested fragments
ES 3.0
Restricted profiles
View Overlays